Conventionally, as a cutting method for glass sheets, there has been widely used a method of cleaving a glass sheet by applying a bending stress to a scribe line formed with a diamond cutter or the like on a surface of the glass sheet (cleaving using a bending stress).
However, in the above-mentioned cutting method using the bending stress, cracks are liable to be formed in cut surfaces, which may lead to a problem that the glass sheet is broken from the cracks. As a countermeasure, instead of the above-mentioned cutting method using the bending stress, in some cases, there has been employed laser fusing for cutting a cutting portion of the glass sheet by melting the cutting portion by using irradiation heat generated by radiating a laser beam to the cutting portion of the glass sheet.
As a cutting method for a glass sheet using the laser fusing, for example, Patent Literature 1 discloses a method in which a glass sheet is fused by radiating a carbon dioxide laser beam obtained by condensing onto a micro spot to a cutting subject portion after being preheated with a defocused carbon dioxide laser beam.
Further, normally, in the laser fusing, a glass substrate is cut (fused) while blowing off melts, which are generated at the cutting portion by irradiation heat of a laser beam, with a center assist gas jetted together with the laser beam substantially vertically downward from just above the cutting portion.
In this case, the melts scattered by the center assist gas may become a foreign matter called dross and adhere to a glass sheet, which constitutes a factor of deterioration in product quality of the glass sheet. Under the circumstances, various measures have been taken to prevent adhesion of such a foreign matter during laser fusing.
For example, although not relating to glass sheet cutting, Patent Literature 2 discloses the following cutting method for preventing adhesion of dross generated at the time of fusing of ceramics and metals. Specifically, the cutting method disclosed in Patent Literature 2 includes: jetting an assist gas (corresponding to the above-mentioned center assist gas) substantially vertically downward from a processing nozzle arranged just above a cutting portion of an object to be processed; scattering a molten foreign matter (such as the dross) toward a waste side of the object to be processed by blowing, from auxiliary nozzles, gases other than the assist gas onto both front and back surfaces of the cutting portion of the object to be processed from the product side thereof; and sucking the molten foreign matter with a suction nozzle just below the cutting portion of the object to be processed.